/**
 * @odoo
 * This file contains 2 modifications from the original 'diff_match_patch.js' file:
 *
 * 1. it has been trimmed to only keep the 'diff' functions (as is), without the
 *    'match' and 'patch' functions, to reduce file size;
 *
 * 2. this comment block has been prepended and an extra 'export' block has been
 *    appended at the end as to make it fit into the Odoo module system.
 */
((exports) => {

/**
 * Diff Match and Patch
 * Copyright 2018 The diff-match-patch Authors.
 * https://github.com/google/diff-match-patch
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @fileoverview Computes the difference between two texts to create a patch.
 * Applies the patch onto another text, allowing for errors.
 * @author fraser@google.com (Neil Fraser)
 */

/**
 * Class containing the diff, match and patch methods.
 * @constructor
 */
var diff_match_patch = function () {
    // Defaults.
    // Redefine these in your program to override the defaults.

    // Number of seconds to map a diff before giving up (0 for infinity).
    this.Diff_Timeout = 1.0;
    // Cost of an empty edit operation in terms of edit characters.
    this.Diff_EditCost = 4;
    // At what point is no match declared (0.0 = perfection, 1.0 = very loose).
    this.Match_Threshold = 0.5;
    // How far to search for a match (0 = exact location, 1000+ = broad match).
    // A match this many characters away from the expected location will add
    // 1.0 to the score (0.0 is a perfect match).
    this.Match_Distance = 1000;
    // When deleting a large block of text (over ~64 characters), how close do
    // the contents have to be to match the expected contents. (0.0 = perfection,
    // 1.0 = very loose).  Note that Match_Threshold controls how closely the
    // end points of a delete need to match.
    this.Patch_DeleteThreshold = 0.5;
    // Chunk size for context length.
    this.Patch_Margin = 4;

    // The number of bits in an int.
    this.Match_MaxBits = 32;
};

//  DIFF FUNCTIONS

/**
 * The data structure representing a diff is an array of tuples:
 * [[DIFF_DELETE, 'Hello'], [DIFF_INSERT, 'Goodbye'], [DIFF_EQUAL, ' world.']]
 * which means: delete 'Hello', add 'Goodbye' and keep ' world.'
 */
var DIFF_DELETE = -1;
var DIFF_INSERT = 1;
var DIFF_EQUAL = 0;

/**
 * Class representing one diff tuple.
 * Attempts to look like a two-element array (which is what this used to be).
 * @param {number} op Operation, one of: DIFF_DELETE, DIFF_INSERT, DIFF_EQUAL.
 * @param {string} text Text to be deleted, inserted, or retained.
 * @constructor
 */
diff_match_patch.Diff = function (op, text) {
    this[0] = op;
    this[1] = text;
};

diff_match_patch.Diff.prototype.length = 2;

/**
 * Emulate the output of a two-element array.
 * @return {string} Diff operation as a string.
 */
diff_match_patch.Diff.prototype.toString = function () {
    return this[0] + "," + this[1];
};

/**
 * Find the differences between two texts.  Simplifies the problem by stripping
 * any common prefix or suffix off the texts before diffing.
 * @param {string} text1 Old string to be diffed.
 * @param {string} text2 New string to be diffed.
 * @param {boolean=} opt_checklines Optional speedup flag. If present and false,
 *     then don't run a line-level diff first to identify the changed areas.
 *     Defaults to true, which does a faster, slightly less optimal diff.
 * @param {number=} opt_deadline Optional time when the diff should be complete
 *     by.  Used internally for recursive calls.  Users should set DiffTimeout
 *     instead.
 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
 */
diff_match_patch.prototype.diff_main = function (text1, text2, opt_checklines, opt_deadline) {
    // Set a deadline by which time the diff must be complete.
    if (typeof opt_deadline == "undefined") {
        if (this.Diff_Timeout <= 0) {
            opt_deadline = Number.MAX_VALUE;
        } else {
            opt_deadline = new Date().getTime() + this.Diff_Timeout * 1000;
        }
    }
    var deadline = opt_deadline;

    // Check for null inputs.
    if (text1 == null || text2 == null) {
        throw new Error("Null input. (diff_main)");
    }

    // Check for equality (speedup).
    if (text1 == text2) {
        if (text1) {
            return [new diff_match_patch.Diff(DIFF_EQUAL, text1)];
        }
        return [];
    }

    if (typeof opt_checklines == "undefined") {
        opt_checklines = true;
    }
    var checklines = opt_checklines;

    // Trim off common prefix (speedup).
    var commonlength = this.diff_commonPrefix(text1, text2);
    var commonprefix = text1.substring(0, commonlength);
    text1 = text1.substring(commonlength);
    text2 = text2.substring(commonlength);

    // Trim off common suffix (speedup).
    commonlength = this.diff_commonSuffix(text1, text2);
    var commonsuffix = text1.substring(text1.length - commonlength);
    text1 = text1.substring(0, text1.length - commonlength);
    text2 = text2.substring(0, text2.length - commonlength);

    // Compute the diff on the middle block.
    var diffs = this.diff_compute_(text1, text2, checklines, deadline);

    // Restore the prefix and suffix.
    if (commonprefix) {
        diffs.unshift(new diff_match_patch.Diff(DIFF_EQUAL, commonprefix));
    }
    if (commonsuffix) {
        diffs.push(new diff_match_patch.Diff(DIFF_EQUAL, commonsuffix));
    }
    this.diff_cleanupMerge(diffs);
    return diffs;
};

/**
 * Find the differences between two texts.  Assumes that the texts do not
 * have any common prefix or suffix.
 * @param {string} text1 Old string to be diffed.
 * @param {string} text2 New string to be diffed.
 * @param {boolean} checklines Speedup flag.  If false, then don't run a
 *     line-level diff first to identify the changed areas.
 *     If true, then run a faster, slightly less optimal diff.
 * @param {number} deadline Time when the diff should be complete by.
 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
 * @private
 */
diff_match_patch.prototype.diff_compute_ = function (text1, text2, checklines, deadline) {
    var diffs;

    if (!text1) {
        // Just add some text (speedup).
        return [new diff_match_patch.Diff(DIFF_INSERT, text2)];
    }

    if (!text2) {
        // Just delete some text (speedup).
        return [new diff_match_patch.Diff(DIFF_DELETE, text1)];
    }

    var longtext = text1.length > text2.length ? text1 : text2;
    var shorttext = text1.length > text2.length ? text2 : text1;
    var i = longtext.indexOf(shorttext);
    if (i != -1) {
        // Shorter text is inside the longer text (speedup).
        diffs = [
            new diff_match_patch.Diff(DIFF_INSERT, longtext.substring(0, i)),
            new diff_match_patch.Diff(DIFF_EQUAL, shorttext),
            new diff_match_patch.Diff(DIFF_INSERT, longtext.substring(i + shorttext.length)),
        ];
        // Swap insertions for deletions if diff is reversed.
        if (text1.length > text2.length) {
            diffs[0][0] = diffs[2][0] = DIFF_DELETE;
        }
        return diffs;
    }

    if (shorttext.length == 1) {
        // Single character string.
        // After the previous speedup, the character can't be an equality.
        return [
            new diff_match_patch.Diff(DIFF_DELETE, text1),
            new diff_match_patch.Diff(DIFF_INSERT, text2),
        ];
    }

    // Check to see if the problem can be split in two.
    var hm = this.diff_halfMatch_(text1, text2);
    if (hm) {
        // A half-match was found, sort out the return data.
        var text1_a = hm[0];
        var text1_b = hm[1];
        var text2_a = hm[2];
        var text2_b = hm[3];
        var mid_common = hm[4];
        // Send both pairs off for separate processing.
        var diffs_a = this.diff_main(text1_a, text2_a, checklines, deadline);
        var diffs_b = this.diff_main(text1_b, text2_b, checklines, deadline);
        // Merge the results.
        return diffs_a.concat([new diff_match_patch.Diff(DIFF_EQUAL, mid_common)], diffs_b);
    }

    if (checklines && text1.length > 100 && text2.length > 100) {
        return this.diff_lineMode_(text1, text2, deadline);
    }

    return this.diff_bisect_(text1, text2, deadline);
};

/**
 * Do a quick line-level diff on both strings, then rediff the parts for
 * greater accuracy.
 * This speedup can produce non-minimal diffs.
 * @param {string} text1 Old string to be diffed.
 * @param {string} text2 New string to be diffed.
 * @param {number} deadline Time when the diff should be complete by.
 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
 * @private
 */
diff_match_patch.prototype.diff_lineMode_ = function (text1, text2, deadline) {
    // Scan the text on a line-by-line basis first.
    var a = this.diff_linesToChars_(text1, text2);
    text1 = a.chars1;
    text2 = a.chars2;
    var linearray = a.lineArray;

    var diffs = this.diff_main(text1, text2, false, deadline);

    // Convert the diff back to original text.
    this.diff_charsToLines_(diffs, linearray);
    // Eliminate freak matches (e.g. blank lines)
    this.diff_cleanupSemantic(diffs);

    // Rediff any replacement blocks, this time character-by-character.
    // Add a dummy entry at the end.
    diffs.push(new diff_match_patch.Diff(DIFF_EQUAL, ""));
    var pointer = 0;
    var count_delete = 0;
    var count_insert = 0;
    var text_delete = "";
    var text_insert = "";
    while (pointer < diffs.length) {
        switch (diffs[pointer][0]) {
            case DIFF_INSERT:
                count_insert++;
                text_insert += diffs[pointer][1];
                break;
            case DIFF_DELETE:
                count_delete++;
                text_delete += diffs[pointer][1];
                break;
            case DIFF_EQUAL:
                // Upon reaching an equality, check for prior redundancies.
                if (count_delete >= 1 && count_insert >= 1) {
                    // Delete the offending records and add the merged ones.
                    diffs.splice(
                        pointer - count_delete - count_insert,
                        count_delete + count_insert
                    );
                    pointer = pointer - count_delete - count_insert;
                    var subDiff = this.diff_main(text_delete, text_insert, false, deadline);
                    for (var j = subDiff.length - 1; j >= 0; j--) {
                        diffs.splice(pointer, 0, subDiff[j]);
                    }
                    pointer = pointer + subDiff.length;
                }
                count_insert = 0;
                count_delete = 0;
                text_delete = "";
                text_insert = "";
                break;
        }
        pointer++;
    }
    diffs.pop(); // Remove the dummy entry at the end.

    return diffs;
};

/**
 * Find the 'middle snake' of a diff, split the problem in two
 * and return the recursively constructed diff.
 * See Myers 1986 paper: An O(ND) Difference Algorithm and Its Variations.
 * @param {string} text1 Old string to be diffed.
 * @param {string} text2 New string to be diffed.
 * @param {number} deadline Time at which to bail if not yet complete.
 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
 * @private
 */
diff_match_patch.prototype.diff_bisect_ = function (text1, text2, deadline) {
    // Cache the text lengths to prevent multiple calls.
    var text1_length = text1.length;
    var text2_length = text2.length;
    var max_d = Math.ceil((text1_length + text2_length) / 2);
    var v_offset = max_d;
    var v_length = 2 * max_d;
    var v1 = new Array(v_length);
    var v2 = new Array(v_length);
    // Setting all elements to -1 is faster in Chrome & Firefox than mixing
    // integers and undefined.
    for (var x = 0; x < v_length; x++) {
        v1[x] = -1;
        v2[x] = -1;
    }
    v1[v_offset + 1] = 0;
    v2[v_offset + 1] = 0;
    var delta = text1_length - text2_length;
    // If the total number of characters is odd, then the front path will collide
    // with the reverse path.
    var front = delta % 2 != 0;
    // Offsets for start and end of k loop.
    // Prevents mapping of space beyond the grid.
    var k1start = 0;
    var k1end = 0;
    var k2start = 0;
    var k2end = 0;
    for (var d = 0; d < max_d; d++) {
        // Bail out if deadline is reached.
        if (new Date().getTime() > deadline) {
            break;
        }

        // Walk the front path one step.
        for (var k1 = -d + k1start; k1 <= d - k1end; k1 += 2) {
            var k1_offset = v_offset + k1;
            var x1;
            if (k1 == -d || (k1 != d && v1[k1_offset - 1] < v1[k1_offset + 1])) {
                x1 = v1[k1_offset + 1];
            } else {
                x1 = v1[k1_offset - 1] + 1;
            }
            var y1 = x1 - k1;
            while (
                x1 < text1_length &&
                y1 < text2_length &&
                text1.charAt(x1) == text2.charAt(y1)
            ) {
                x1++;
                y1++;
            }
            v1[k1_offset] = x1;
            if (x1 > text1_length) {
                // Ran off the right of the graph.
                k1end += 2;
            } else if (y1 > text2_length) {
                // Ran off the bottom of the graph.
                k1start += 2;
            } else if (front) {
                var k2_offset = v_offset + delta - k1;
                if (k2_offset >= 0 && k2_offset < v_length && v2[k2_offset] != -1) {
                    // Mirror x2 onto top-left coordinate system.
                    var x2 = text1_length - v2[k2_offset];
                    if (x1 >= x2) {
                        // Overlap detected.
                        return this.diff_bisectSplit_(text1, text2, x1, y1, deadline);
                    }
                }
            }
        }

        // Walk the reverse path one step.
        for (var k2 = -d + k2start; k2 <= d - k2end; k2 += 2) {
            var k2_offset = v_offset + k2;
            var x2;
            if (k2 == -d || (k2 != d && v2[k2_offset - 1] < v2[k2_offset + 1])) {
                x2 = v2[k2_offset + 1];
            } else {
                x2 = v2[k2_offset - 1] + 1;
            }
            var y2 = x2 - k2;
            while (
                x2 < text1_length &&
                y2 < text2_length &&
                text1.charAt(text1_length - x2 - 1) == text2.charAt(text2_length - y2 - 1)
            ) {
                x2++;
                y2++;
            }
            v2[k2_offset] = x2;
            if (x2 > text1_length) {
                // Ran off the left of the graph.
                k2end += 2;
            } else if (y2 > text2_length) {
                // Ran off the top of the graph.
                k2start += 2;
            } else if (!front) {
                var k1_offset = v_offset + delta - k2;
                if (k1_offset >= 0 && k1_offset < v_length && v1[k1_offset] != -1) {
                    var x1 = v1[k1_offset];
                    var y1 = v_offset + x1 - k1_offset;
                    // Mirror x2 onto top-left coordinate system.
                    x2 = text1_length - x2;
                    if (x1 >= x2) {
                        // Overlap detected.
                        return this.diff_bisectSplit_(text1, text2, x1, y1, deadline);
                    }
                }
            }
        }
    }
    // Diff took too long and hit the deadline or
    // number of diffs equals number of characters, no commonality at all.
    return [
        new diff_match_patch.Diff(DIFF_DELETE, text1),
        new diff_match_patch.Diff(DIFF_INSERT, text2),
    ];
};

/**
 * Given the location of the 'middle snake', split the diff in two parts
 * and recurse.
 * @param {string} text1 Old string to be diffed.
 * @param {string} text2 New string to be diffed.
 * @param {number} x Index of split point in text1.
 * @param {number} y Index of split point in text2.
 * @param {number} deadline Time at which to bail if not yet complete.
 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
 * @private
 */
diff_match_patch.prototype.diff_bisectSplit_ = function (text1, text2, x, y, deadline) {
    var text1a = text1.substring(0, x);
    var text2a = text2.substring(0, y);
    var text1b = text1.substring(x);
    var text2b = text2.substring(y);

    // Compute both diffs serially.
    var diffs = this.diff_main(text1a, text2a, false, deadline);
    var diffsb = this.diff_main(text1b, text2b, false, deadline);

    return diffs.concat(diffsb);
};

/**
 * Split two texts into an array of strings.  Reduce the texts to a string of
 * hashes where each Unicode character represents one line.
 * @param {string} text1 First string.
 * @param {string} text2 Second string.
 * @return {{chars1: string, chars2: string, lineArray: !Array.<string>}}
 *     An object containing the encoded text1, the encoded text2 and
 *     the array of unique strings.
 *     The zeroth element of the array of unique strings is intentionally blank.
 * @private
 */
diff_match_patch.prototype.diff_linesToChars_ = function (text1, text2) {
    var lineArray = []; // e.g. lineArray[4] == 'Hello\n'
    var lineHash = {}; // e.g. lineHash['Hello\n'] == 4

    // '\x00' is a valid character, but various debuggers don't like it.
    // So we'll insert a junk entry to avoid generating a null character.
    lineArray[0] = "";

    /**
     * Split a text into an array of strings.  Reduce the texts to a string of
     * hashes where each Unicode character represents one line.
     * Modifies linearray and linehash through being a closure.
     * @param {string} text String to encode.
     * @return {string} Encoded string.
     * @private
     */
    function diff_linesToCharsMunge_(text) {
        var chars = "";
        // Walk the text, pulling out a substring for each line.
        // text.split('\n') would would temporarily double our memory footprint.
        // Modifying text would create many large strings to garbage collect.
        var lineStart = 0;
        var lineEnd = -1;
        // Keeping our own length variable is faster than looking it up.
        var lineArrayLength = lineArray.length;
        while (lineEnd < text.length - 1) {
            lineEnd = text.indexOf("\n", lineStart);
            if (lineEnd == -1) {
                lineEnd = text.length - 1;
            }
            var line = text.substring(lineStart, lineEnd + 1);

            if (
                lineHash.hasOwnProperty
                    ? lineHash.hasOwnProperty(line)
                    : lineHash[line] !== undefined
            ) {
                chars += String.fromCharCode(lineHash[line]);
            } else {
                if (lineArrayLength == maxLines) {
                    // Bail out at 65535 because
                    // String.fromCharCode(65536) == String.fromCharCode(0)
                    line = text.substring(lineStart);
                    lineEnd = text.length;
                }
                chars += String.fromCharCode(lineArrayLength);
                lineHash[line] = lineArrayLength;
                lineArray[lineArrayLength++] = line;
            }
            lineStart = lineEnd + 1;
        }
        return chars;
    }
    // Allocate 2/3rds of the space for text1, the rest for text2.
    var maxLines = 40000;
    var chars1 = diff_linesToCharsMunge_(text1);
    maxLines = 65535;
    var chars2 = diff_linesToCharsMunge_(text2);
    return { chars1: chars1, chars2: chars2, lineArray: lineArray };
};

/**
 * Rehydrate the text in a diff from a string of line hashes to real lines of
 * text.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 * @param {!Array.<string>} lineArray Array of unique strings.
 * @private
 */
diff_match_patch.prototype.diff_charsToLines_ = function (diffs, lineArray) {
    for (var i = 0; i < diffs.length; i++) {
        var chars = diffs[i][1];
        var text = [];
        for (var j = 0; j < chars.length; j++) {
            text[j] = lineArray[chars.charCodeAt(j)];
        }
        diffs[i][1] = text.join("");
    }
};

/**
 * Determine the common prefix of two strings.
 * @param {string} text1 First string.
 * @param {string} text2 Second string.
 * @return {number} The number of characters common to the start of each
 *     string.
 */
diff_match_patch.prototype.diff_commonPrefix = function (text1, text2) {
    // Quick check for common null cases.
    if (!text1 || !text2 || text1.charAt(0) != text2.charAt(0)) {
        return 0;
    }
    // Binary search.
    // Performance analysis: https://neil.fraser.name/news/2007/10/09/
    var pointermin = 0;
    var pointermax = Math.min(text1.length, text2.length);
    var pointermid = pointermax;
    var pointerstart = 0;
    while (pointermin < pointermid) {
        if (
            text1.substring(pointerstart, pointermid) ==
            text2.substring(pointerstart, pointermid)
        ) {
            pointermin = pointermid;
            pointerstart = pointermin;
        } else {
            pointermax = pointermid;
        }
        pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
    }
    return pointermid;
};

/**
 * Determine the common suffix of two strings.
 * @param {string} text1 First string.
 * @param {string} text2 Second string.
 * @return {number} The number of characters common to the end of each string.
 */
diff_match_patch.prototype.diff_commonSuffix = function (text1, text2) {
    // Quick check for common null cases.
    if (!text1 || !text2 || text1.charAt(text1.length - 1) != text2.charAt(text2.length - 1)) {
        return 0;
    }
    // Binary search.
    // Performance analysis: https://neil.fraser.name/news/2007/10/09/
    var pointermin = 0;
    var pointermax = Math.min(text1.length, text2.length);
    var pointermid = pointermax;
    var pointerend = 0;
    while (pointermin < pointermid) {
        if (
            text1.substring(text1.length - pointermid, text1.length - pointerend) ==
            text2.substring(text2.length - pointermid, text2.length - pointerend)
        ) {
            pointermin = pointermid;
            pointerend = pointermin;
        } else {
            pointermax = pointermid;
        }
        pointermid = Math.floor((pointermax - pointermin) / 2 + pointermin);
    }
    return pointermid;
};

/**
 * Determine if the suffix of one string is the prefix of another.
 * @param {string} text1 First string.
 * @param {string} text2 Second string.
 * @return {number} The number of characters common to the end of the first
 *     string and the start of the second string.
 * @private
 */
diff_match_patch.prototype.diff_commonOverlap_ = function (text1, text2) {
    // Cache the text lengths to prevent multiple calls.
    var text1_length = text1.length;
    var text2_length = text2.length;
    // Eliminate the null case.
    if (text1_length == 0 || text2_length == 0) {
        return 0;
    }
    // Truncate the longer string.
    if (text1_length > text2_length) {
        text1 = text1.substring(text1_length - text2_length);
    } else if (text1_length < text2_length) {
        text2 = text2.substring(0, text1_length);
    }
    var text_length = Math.min(text1_length, text2_length);
    // Quick check for the worst case.
    if (text1 == text2) {
        return text_length;
    }

    // Start by looking for a single character match
    // and increase length until no match is found.
    // Performance analysis: https://neil.fraser.name/news/2010/11/04/
    var best = 0;
    var length = 1;
    while (true) {
        var pattern = text1.substring(text_length - length);
        var found = text2.indexOf(pattern);
        if (found == -1) {
            return best;
        }
        length += found;
        if (found == 0 || text1.substring(text_length - length) == text2.substring(0, length)) {
            best = length;
            length++;
        }
    }
};

/**
 * Do the two texts share a substring which is at least half the length of the
 * longer text?
 * This speedup can produce non-minimal diffs.
 * @param {string} text1 First string.
 * @param {string} text2 Second string.
 * @return {Array.<string>} Five element Array, containing the prefix of
 *     text1, the suffix of text1, the prefix of text2, the suffix of
 *     text2 and the common middle.  Or null if there was no match.
 * @private
 */
diff_match_patch.prototype.diff_halfMatch_ = function (text1, text2) {
    if (this.Diff_Timeout <= 0) {
        // Don't risk returning a non-optimal diff if we have unlimited time.
        return null;
    }
    var longtext = text1.length > text2.length ? text1 : text2;
    var shorttext = text1.length > text2.length ? text2 : text1;
    if (longtext.length < 4 || shorttext.length * 2 < longtext.length) {
        return null; // Pointless.
    }
    var dmp = this; // 'this' becomes 'window' in a closure.

    /**
     * Does a substring of shorttext exist within longtext such that the substring
     * is at least half the length of longtext?
     * Closure, but does not reference any external variables.
     * @param {string} longtext Longer string.
     * @param {string} shorttext Shorter string.
     * @param {number} i Start index of quarter length substring within longtext.
     * @return {Array.<string>} Five element Array, containing the prefix of
     *     longtext, the suffix of longtext, the prefix of shorttext, the suffix
     *     of shorttext and the common middle.  Or null if there was no match.
     * @private
     */
    function diff_halfMatchI_(longtext, shorttext, i) {
        // Start with a 1/4 length substring at position i as a seed.
        var seed = longtext.substring(i, i + Math.floor(longtext.length / 4));
        var j = -1;
        var best_common = "";
        var best_longtext_a, best_longtext_b, best_shorttext_a, best_shorttext_b;
        while ((j = shorttext.indexOf(seed, j + 1)) != -1) {
            var prefixLength = dmp.diff_commonPrefix(
                longtext.substring(i),
                shorttext.substring(j)
            );
            var suffixLength = dmp.diff_commonSuffix(
                longtext.substring(0, i),
                shorttext.substring(0, j)
            );
            if (best_common.length < suffixLength + prefixLength) {
                best_common =
                    shorttext.substring(j - suffixLength, j) +
                    shorttext.substring(j, j + prefixLength);
                best_longtext_a = longtext.substring(0, i - suffixLength);
                best_longtext_b = longtext.substring(i + prefixLength);
                best_shorttext_a = shorttext.substring(0, j - suffixLength);
                best_shorttext_b = shorttext.substring(j + prefixLength);
            }
        }
        if (best_common.length * 2 >= longtext.length) {
            return [
                best_longtext_a,
                best_longtext_b,
                best_shorttext_a,
                best_shorttext_b,
                best_common,
            ];
        } else {
            return null;
        }
    }

    // First check if the second quarter is the seed for a half-match.
    var hm1 = diff_halfMatchI_(longtext, shorttext, Math.ceil(longtext.length / 4));
    // Check again based on the third quarter.
    var hm2 = diff_halfMatchI_(longtext, shorttext, Math.ceil(longtext.length / 2));
    var hm;
    if (!hm1 && !hm2) {
        return null;
    } else if (!hm2) {
        hm = hm1;
    } else if (!hm1) {
        hm = hm2;
    } else {
        // Both matched.  Select the longest.
        hm = hm1[4].length > hm2[4].length ? hm1 : hm2;
    }

    // A half-match was found, sort out the return data.
    var text1_a, text1_b, text2_a, text2_b;
    if (text1.length > text2.length) {
        text1_a = hm[0];
        text1_b = hm[1];
        text2_a = hm[2];
        text2_b = hm[3];
    } else {
        text2_a = hm[0];
        text2_b = hm[1];
        text1_a = hm[2];
        text1_b = hm[3];
    }
    var mid_common = hm[4];
    return [text1_a, text1_b, text2_a, text2_b, mid_common];
};

/**
 * Reduce the number of edits by eliminating semantically trivial equalities.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 */
diff_match_patch.prototype.diff_cleanupSemantic = function (diffs) {
    var changes = false;
    var equalities = []; // Stack of indices where equalities are found.
    var equalitiesLength = 0; // Keeping our own length var is faster in JS.
    /** @type {?string} */
    var lastEquality = null;
    // Always equal to diffs[equalities[equalitiesLength - 1]][1]
    var pointer = 0; // Index of current position.
    // Number of characters that changed prior to the equality.
    var length_insertions1 = 0;
    var length_deletions1 = 0;
    // Number of characters that changed after the equality.
    var length_insertions2 = 0;
    var length_deletions2 = 0;
    while (pointer < diffs.length) {
        if (diffs[pointer][0] == DIFF_EQUAL) {
            // Equality found.
            equalities[equalitiesLength++] = pointer;
            length_insertions1 = length_insertions2;
            length_deletions1 = length_deletions2;
            length_insertions2 = 0;
            length_deletions2 = 0;
            lastEquality = diffs[pointer][1];
        } else {
            // An insertion or deletion.
            if (diffs[pointer][0] == DIFF_INSERT) {
                length_insertions2 += diffs[pointer][1].length;
            } else {
                length_deletions2 += diffs[pointer][1].length;
            }
            // Eliminate an equality that is smaller or equal to the edits on both
            // sides of it.
            if (
                lastEquality &&
                lastEquality.length <= Math.max(length_insertions1, length_deletions1) &&
                lastEquality.length <= Math.max(length_insertions2, length_deletions2)
            ) {
                // Duplicate record.
                diffs.splice(
                    equalities[equalitiesLength - 1],
                    0,
                    new diff_match_patch.Diff(DIFF_DELETE, lastEquality)
                );
                // Change second copy to insert.
                diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT;
                // Throw away the equality we just deleted.
                equalitiesLength--;
                // Throw away the previous equality (it needs to be reevaluated).
                equalitiesLength--;
                pointer = equalitiesLength > 0 ? equalities[equalitiesLength - 1] : -1;
                length_insertions1 = 0; // Reset the counters.
                length_deletions1 = 0;
                length_insertions2 = 0;
                length_deletions2 = 0;
                lastEquality = null;
                changes = true;
            }
        }
        pointer++;
    }

    // Normalize the diff.
    if (changes) {
        this.diff_cleanupMerge(diffs);
    }
    this.diff_cleanupSemanticLossless(diffs);

    // Find any overlaps between deletions and insertions.
    // e.g: <del>abcxxx</del><ins>xxxdef</ins>
    //   -> <del>abc</del>xxx<ins>def</ins>
    // e.g: <del>xxxabc</del><ins>defxxx</ins>
    //   -> <ins>def</ins>xxx<del>abc</del>
    // Only extract an overlap if it is as big as the edit ahead or behind it.
    pointer = 1;
    while (pointer < diffs.length) {
        if (diffs[pointer - 1][0] == DIFF_DELETE && diffs[pointer][0] == DIFF_INSERT) {
            var deletion = diffs[pointer - 1][1];
            var insertion = diffs[pointer][1];
            var overlap_length1 = this.diff_commonOverlap_(deletion, insertion);
            var overlap_length2 = this.diff_commonOverlap_(insertion, deletion);
            if (overlap_length1 >= overlap_length2) {
                if (
                    overlap_length1 >= deletion.length / 2 ||
                    overlap_length1 >= insertion.length / 2
                ) {
                    // Overlap found.  Insert an equality and trim the surrounding edits.
                    diffs.splice(
                        pointer,
                        0,
                        new diff_match_patch.Diff(
                            DIFF_EQUAL,
                            insertion.substring(0, overlap_length1)
                        )
                    );
                    diffs[pointer - 1][1] = deletion.substring(
                        0,
                        deletion.length - overlap_length1
                    );
                    diffs[pointer + 1][1] = insertion.substring(overlap_length1);
                    pointer++;
                }
            } else {
                if (
                    overlap_length2 >= deletion.length / 2 ||
                    overlap_length2 >= insertion.length / 2
                ) {
                    // Reverse overlap found.
                    // Insert an equality and swap and trim the surrounding edits.
                    diffs.splice(
                        pointer,
                        0,
                        new diff_match_patch.Diff(
                            DIFF_EQUAL,
                            deletion.substring(0, overlap_length2)
                        )
                    );
                    diffs[pointer - 1][0] = DIFF_INSERT;
                    diffs[pointer - 1][1] = insertion.substring(
                        0,
                        insertion.length - overlap_length2
                    );
                    diffs[pointer + 1][0] = DIFF_DELETE;
                    diffs[pointer + 1][1] = deletion.substring(overlap_length2);
                    pointer++;
                }
            }
            pointer++;
        }
        pointer++;
    }
};

/**
 * Look for single edits surrounded on both sides by equalities
 * which can be shifted sideways to align the edit to a word boundary.
 * e.g: The c<ins>at c</ins>ame. -> The <ins>cat </ins>came.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 */
diff_match_patch.prototype.diff_cleanupSemanticLossless = function (diffs) {
    /**
     * Given two strings, compute a score representing whether the internal
     * boundary falls on logical boundaries.
     * Scores range from 6 (best) to 0 (worst).
     * Closure, but does not reference any external variables.
     * @param {string} one First string.
     * @param {string} two Second string.
     * @return {number} The score.
     * @private
     */
    function diff_cleanupSemanticScore_(one, two) {
        if (!one || !two) {
            // Edges are the best.
            return 6;
        }

        // Each port of this function behaves slightly differently due to
        // subtle differences in each language's definition of things like
        // 'whitespace'.  Since this function's purpose is largely cosmetic,
        // the choice has been made to use each language's native features
        // rather than force total conformity.
        var char1 = one.charAt(one.length - 1);
        var char2 = two.charAt(0);
        var nonAlphaNumeric1 = char1.match(diff_match_patch.nonAlphaNumericRegex_);
        var nonAlphaNumeric2 = char2.match(diff_match_patch.nonAlphaNumericRegex_);
        var whitespace1 = nonAlphaNumeric1 && char1.match(diff_match_patch.whitespaceRegex_);
        var whitespace2 = nonAlphaNumeric2 && char2.match(diff_match_patch.whitespaceRegex_);
        var lineBreak1 = whitespace1 && char1.match(diff_match_patch.linebreakRegex_);
        var lineBreak2 = whitespace2 && char2.match(diff_match_patch.linebreakRegex_);
        var blankLine1 = lineBreak1 && one.match(diff_match_patch.blanklineEndRegex_);
        var blankLine2 = lineBreak2 && two.match(diff_match_patch.blanklineStartRegex_);

        if (blankLine1 || blankLine2) {
            // Five points for blank lines.
            return 5;
        } else if (lineBreak1 || lineBreak2) {
            // Four points for line breaks.
            return 4;
        } else if (nonAlphaNumeric1 && !whitespace1 && whitespace2) {
            // Three points for end of sentences.
            return 3;
        } else if (whitespace1 || whitespace2) {
            // Two points for whitespace.
            return 2;
        } else if (nonAlphaNumeric1 || nonAlphaNumeric2) {
            // One point for non-alphanumeric.
            return 1;
        }
        return 0;
    }

    var pointer = 1;
    // Intentionally ignore the first and last element (don't need checking).
    while (pointer < diffs.length - 1) {
        if (diffs[pointer - 1][0] == DIFF_EQUAL && diffs[pointer + 1][0] == DIFF_EQUAL) {
            // This is a single edit surrounded by equalities.
            var equality1 = diffs[pointer - 1][1];
            var edit = diffs[pointer][1];
            var equality2 = diffs[pointer + 1][1];

            // First, shift the edit as far left as possible.
            var commonOffset = this.diff_commonSuffix(equality1, edit);
            if (commonOffset) {
                var commonString = edit.substring(edit.length - commonOffset);
                equality1 = equality1.substring(0, equality1.length - commonOffset);
                edit = commonString + edit.substring(0, edit.length - commonOffset);
                equality2 = commonString + equality2;
            }

            // Second, step character by character right, looking for the best fit.
            var bestEquality1 = equality1;
            var bestEdit = edit;
            var bestEquality2 = equality2;
            var bestScore =
                diff_cleanupSemanticScore_(equality1, edit) +
                diff_cleanupSemanticScore_(edit, equality2);
            while (edit.charAt(0) === equality2.charAt(0)) {
                equality1 += edit.charAt(0);
                edit = edit.substring(1) + equality2.charAt(0);
                equality2 = equality2.substring(1);
                var score =
                    diff_cleanupSemanticScore_(equality1, edit) +
                    diff_cleanupSemanticScore_(edit, equality2);
                // The >= encourages trailing rather than leading whitespace on edits.
                if (score >= bestScore) {
                    bestScore = score;
                    bestEquality1 = equality1;
                    bestEdit = edit;
                    bestEquality2 = equality2;
                }
            }

            if (diffs[pointer - 1][1] != bestEquality1) {
                // We have an improvement, save it back to the diff.
                if (bestEquality1) {
                    diffs[pointer - 1][1] = bestEquality1;
                } else {
                    diffs.splice(pointer - 1, 1);
                    pointer--;
                }
                diffs[pointer][1] = bestEdit;
                if (bestEquality2) {
                    diffs[pointer + 1][1] = bestEquality2;
                } else {
                    diffs.splice(pointer + 1, 1);
                    pointer--;
                }
            }
        }
        pointer++;
    }
};

// Define some regex patterns for matching boundaries.
diff_match_patch.nonAlphaNumericRegex_ = /[^a-zA-Z0-9]/;
diff_match_patch.whitespaceRegex_ = /\s/;
diff_match_patch.linebreakRegex_ = /[\r\n]/;
diff_match_patch.blanklineEndRegex_ = /\n\r?\n$/;
diff_match_patch.blanklineStartRegex_ = /^\r?\n\r?\n/;

/**
 * Reduce the number of edits by eliminating operationally trivial equalities.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 */
diff_match_patch.prototype.diff_cleanupEfficiency = function (diffs) {
    var changes = false;
    var equalities = []; // Stack of indices where equalities are found.
    var equalitiesLength = 0; // Keeping our own length var is faster in JS.
    /** @type {?string} */
    var lastEquality = null;
    // Always equal to diffs[equalities[equalitiesLength - 1]][1]
    var pointer = 0; // Index of current position.
    // Is there an insertion operation before the last equality.
    var pre_ins = false;
    // Is there a deletion operation before the last equality.
    var pre_del = false;
    // Is there an insertion operation after the last equality.
    var post_ins = false;
    // Is there a deletion operation after the last equality.
    var post_del = false;
    while (pointer < diffs.length) {
        if (diffs[pointer][0] == DIFF_EQUAL) {
            // Equality found.
            if (diffs[pointer][1].length < this.Diff_EditCost && (post_ins || post_del)) {
                // Candidate found.
                equalities[equalitiesLength++] = pointer;
                pre_ins = post_ins;
                pre_del = post_del;
                lastEquality = diffs[pointer][1];
            } else {
                // Not a candidate, and can never become one.
                equalitiesLength = 0;
                lastEquality = null;
            }
            post_ins = post_del = false;
        } else {
            // An insertion or deletion.
            if (diffs[pointer][0] == DIFF_DELETE) {
                post_del = true;
            } else {
                post_ins = true;
            }
            /*
                * Five types to be split:
                * <ins>A</ins><del>B</del>XY<ins>C</ins><del>D</del>
                * <ins>A</ins>X<ins>C</ins><del>D</del>
                * <ins>A</ins><del>B</del>X<ins>C</ins>
                * <ins>A</del>X<ins>C</ins><del>D</del>
                * <ins>A</ins><del>B</del>X<del>C</del>
                */
            if (
                lastEquality &&
                ((pre_ins && pre_del && post_ins && post_del) ||
                    (lastEquality.length < this.Diff_EditCost / 2 &&
                        pre_ins + pre_del + post_ins + post_del == 3))
            ) {
                // Duplicate record.
                diffs.splice(
                    equalities[equalitiesLength - 1],
                    0,
                    new diff_match_patch.Diff(DIFF_DELETE, lastEquality)
                );
                // Change second copy to insert.
                diffs[equalities[equalitiesLength - 1] + 1][0] = DIFF_INSERT;
                equalitiesLength--; // Throw away the equality we just deleted;
                lastEquality = null;
                if (pre_ins && pre_del) {
                    // No changes made which could affect previous entry, keep going.
                    post_ins = post_del = true;
                    equalitiesLength = 0;
                } else {
                    equalitiesLength--; // Throw away the previous equality.
                    pointer = equalitiesLength > 0 ? equalities[equalitiesLength - 1] : -1;
                    post_ins = post_del = false;
                }
                changes = true;
            }
        }
        pointer++;
    }

    if (changes) {
        this.diff_cleanupMerge(diffs);
    }
};

/**
 * Reorder and merge like edit sections.  Merge equalities.
 * Any edit section can move as long as it doesn't cross an equality.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 */
diff_match_patch.prototype.diff_cleanupMerge = function (diffs) {
    // Add a dummy entry at the end.
    diffs.push(new diff_match_patch.Diff(DIFF_EQUAL, ""));
    var pointer = 0;
    var count_delete = 0;
    var count_insert = 0;
    var text_delete = "";
    var text_insert = "";
    var commonlength;
    while (pointer < diffs.length) {
        switch (diffs[pointer][0]) {
            case DIFF_INSERT:
                count_insert++;
                text_insert += diffs[pointer][1];
                pointer++;
                break;
            case DIFF_DELETE:
                count_delete++;
                text_delete += diffs[pointer][1];
                pointer++;
                break;
            case DIFF_EQUAL:
                // Upon reaching an equality, check for prior redundancies.
                if (count_delete + count_insert > 1) {
                    if (count_delete !== 0 && count_insert !== 0) {
                        // Factor out any common prefixies.
                        commonlength = this.diff_commonPrefix(text_insert, text_delete);
                        if (commonlength !== 0) {
                            if (
                                pointer - count_delete - count_insert > 0 &&
                                diffs[pointer - count_delete - count_insert - 1][0] ==
                                    DIFF_EQUAL
                            ) {
                                diffs[pointer - count_delete - count_insert - 1][1] +=
                                    text_insert.substring(0, commonlength);
                            } else {
                                diffs.splice(
                                    0,
                                    0,
                                    new diff_match_patch.Diff(
                                        DIFF_EQUAL,
                                        text_insert.substring(0, commonlength)
                                    )
                                );
                                pointer++;
                            }
                            text_insert = text_insert.substring(commonlength);
                            text_delete = text_delete.substring(commonlength);
                        }
                        // Factor out any common suffixies.
                        commonlength = this.diff_commonSuffix(text_insert, text_delete);
                        if (commonlength !== 0) {
                            diffs[pointer][1] =
                                text_insert.substring(text_insert.length - commonlength) +
                                diffs[pointer][1];
                            text_insert = text_insert.substring(
                                0,
                                text_insert.length - commonlength
                            );
                            text_delete = text_delete.substring(
                                0,
                                text_delete.length - commonlength
                            );
                        }
                    }
                    // Delete the offending records and add the merged ones.
                    pointer -= count_delete + count_insert;
                    diffs.splice(pointer, count_delete + count_insert);
                    if (text_delete.length) {
                        diffs.splice(
                            pointer,
                            0,
                            new diff_match_patch.Diff(DIFF_DELETE, text_delete)
                        );
                        pointer++;
                    }
                    if (text_insert.length) {
                        diffs.splice(
                            pointer,
                            0,
                            new diff_match_patch.Diff(DIFF_INSERT, text_insert)
                        );
                        pointer++;
                    }
                    pointer++;
                } else if (pointer !== 0 && diffs[pointer - 1][0] == DIFF_EQUAL) {
                    // Merge this equality with the previous one.
                    diffs[pointer - 1][1] += diffs[pointer][1];
                    diffs.splice(pointer, 1);
                } else {
                    pointer++;
                }
                count_insert = 0;
                count_delete = 0;
                text_delete = "";
                text_insert = "";
                break;
        }
    }
    if (diffs[diffs.length - 1][1] === "") {
        diffs.pop(); // Remove the dummy entry at the end.
    }

    // Second pass: look for single edits surrounded on both sides by equalities
    // which can be shifted sideways to eliminate an equality.
    // e.g: A<ins>BA</ins>C -> <ins>AB</ins>AC
    var changes = false;
    pointer = 1;
    // Intentionally ignore the first and last element (don't need checking).
    while (pointer < diffs.length - 1) {
        if (diffs[pointer - 1][0] == DIFF_EQUAL && diffs[pointer + 1][0] == DIFF_EQUAL) {
            // This is a single edit surrounded by equalities.
            if (
                diffs[pointer][1].substring(
                    diffs[pointer][1].length - diffs[pointer - 1][1].length
                ) == diffs[pointer - 1][1]
            ) {
                // Shift the edit over the previous equality.
                diffs[pointer][1] =
                    diffs[pointer - 1][1] +
                    diffs[pointer][1].substring(
                        0,
                        diffs[pointer][1].length - diffs[pointer - 1][1].length
                    );
                diffs[pointer + 1][1] = diffs[pointer - 1][1] + diffs[pointer + 1][1];
                diffs.splice(pointer - 1, 1);
                changes = true;
            } else if (
                diffs[pointer][1].substring(0, diffs[pointer + 1][1].length) ==
                diffs[pointer + 1][1]
            ) {
                // Shift the edit over the next equality.
                diffs[pointer - 1][1] += diffs[pointer + 1][1];
                diffs[pointer][1] =
                    diffs[pointer][1].substring(diffs[pointer + 1][1].length) +
                    diffs[pointer + 1][1];
                diffs.splice(pointer + 1, 1);
                changes = true;
            }
        }
        pointer++;
    }
    // If shifts were made, the diff needs reordering and another shift sweep.
    if (changes) {
        this.diff_cleanupMerge(diffs);
    }
};

/**
 * loc is a location in text1, compute and return the equivalent location in
 * text2.
 * e.g. 'The cat' vs 'The big cat', 1->1, 5->8
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 * @param {number} loc Location within text1.
 * @return {number} Location within text2.
 */
diff_match_patch.prototype.diff_xIndex = function (diffs, loc) {
    var chars1 = 0;
    var chars2 = 0;
    var last_chars1 = 0;
    var last_chars2 = 0;
    var x;
    for (x = 0; x < diffs.length; x++) {
        if (diffs[x][0] !== DIFF_INSERT) {
            // Equality or deletion.
            chars1 += diffs[x][1].length;
        }
        if (diffs[x][0] !== DIFF_DELETE) {
            // Equality or insertion.
            chars2 += diffs[x][1].length;
        }
        if (chars1 > loc) {
            // Overshot the location.
            break;
        }
        last_chars1 = chars1;
        last_chars2 = chars2;
    }
    // Was the location was deleted?
    if (diffs.length != x && diffs[x][0] === DIFF_DELETE) {
        return last_chars2;
    }
    // Add the remaining character length.
    return last_chars2 + (loc - last_chars1);
};

/**
 * Convert a diff array into a pretty HTML report.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 * @return {string} HTML representation.
 */
diff_match_patch.prototype.diff_prettyHtml = function (diffs) {
    var html = [];
    var pattern_amp = /&/g;
    var pattern_lt = /</g;
    var pattern_gt = />/g;
    var pattern_para = /\n/g;
    for (var x = 0; x < diffs.length; x++) {
        var op = diffs[x][0]; // Operation (insert, delete, equal)
        var data = diffs[x][1]; // Text of change.
        var text = data
            .replace(pattern_amp, "&amp;")
            .replace(pattern_lt, "&lt;")
            .replace(pattern_gt, "&gt;")
            .replace(pattern_para, "&para;<br>");
        switch (op) {
            case DIFF_INSERT:
                html[x] = '<ins style="background:#e6ffe6;">' + text + "</ins>";
                break;
            case DIFF_DELETE:
                html[x] = '<del style="background:#ffe6e6;">' + text + "</del>";
                break;
            case DIFF_EQUAL:
                html[x] = "<span>" + text + "</span>";
                break;
        }
    }
    return html.join("");
};

/**
 * Compute and return the source text (all equalities and deletions).
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 * @return {string} Source text.
 */
diff_match_patch.prototype.diff_text1 = function (diffs) {
    var text = [];
    for (var x = 0; x < diffs.length; x++) {
        if (diffs[x][0] !== DIFF_INSERT) {
            text[x] = diffs[x][1];
        }
    }
    return text.join("");
};

/**
 * Compute and return the destination text (all equalities and insertions).
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 * @return {string} Destination text.
 */
diff_match_patch.prototype.diff_text2 = function (diffs) {
    var text = [];
    for (var x = 0; x < diffs.length; x++) {
        if (diffs[x][0] !== DIFF_DELETE) {
            text[x] = diffs[x][1];
        }
    }
    return text.join("");
};

/**
 * Compute the Levenshtein distance; the number of inserted, deleted or
 * substituted characters.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 * @return {number} Number of changes.
 */
diff_match_patch.prototype.diff_levenshtein = function (diffs) {
    var levenshtein = 0;
    var insertions = 0;
    var deletions = 0;
    for (var x = 0; x < diffs.length; x++) {
        var op = diffs[x][0];
        var data = diffs[x][1];
        switch (op) {
            case DIFF_INSERT:
                insertions += data.length;
                break;
            case DIFF_DELETE:
                deletions += data.length;
                break;
            case DIFF_EQUAL:
                // A deletion and an insertion is one substitution.
                levenshtein += Math.max(insertions, deletions);
                insertions = 0;
                deletions = 0;
                break;
        }
    }
    levenshtein += Math.max(insertions, deletions);
    return levenshtein;
};

/**
 * Crush the diff into an encoded string which describes the operations
 * required to transform text1 into text2.
 * E.g. =3\t-2\t+ing  -> Keep 3 chars, delete 2 chars, insert 'ing'.
 * Operations are tab-separated.  Inserted text is escaped using %xx notation.
 * @param {!Array.<!diff_match_patch.Diff>} diffs Array of diff tuples.
 * @return {string} Delta text.
 */
diff_match_patch.prototype.diff_toDelta = function (diffs) {
    var text = [];
    for (var x = 0; x < diffs.length; x++) {
        switch (diffs[x][0]) {
            case DIFF_INSERT:
                text[x] = "+" + encodeURI(diffs[x][1]);
                break;
            case DIFF_DELETE:
                text[x] = "-" + diffs[x][1].length;
                break;
            case DIFF_EQUAL:
                text[x] = "=" + diffs[x][1].length;
                break;
        }
    }
    return text.join("\t").replace(/%20/g, " ");
};

/**
 * Given the original text1, and an encoded string which describes the
 * operations required to transform text1 into text2, compute the full diff.
 * @param {string} text1 Source string for the diff.
 * @param {string} delta Delta text.
 * @return {!Array.<!diff_match_patch.Diff>} Array of diff tuples.
 * @throws {!Error} If invalid input.
 */
diff_match_patch.prototype.diff_fromDelta = function (text1, delta) {
    var diffs = [];
    var diffsLength = 0; // Keeping our own length var is faster in JS.
    var pointer = 0; // Cursor in text1
    var tokens = delta.split(/\t/g);
    for (var x = 0; x < tokens.length; x++) {
        // Each token begins with a one character parameter which specifies the
        // operation of this token (delete, insert, equality).
        var param = tokens[x].substring(1);
        switch (tokens[x].charAt(0)) {
            case "+":
                try {
                    diffs[diffsLength++] = new diff_match_patch.Diff(
                        DIFF_INSERT,
                        decodeURI(param)
                    );
                } catch (ex) {
                    // Malformed URI sequence.
                    throw new Error("Illegal escape in diff_fromDelta: " + param);
                }
                break;
            case "-":
            // Fall through.
            case "=":
                var n = parseInt(param, 10);
                if (isNaN(n) || n < 0) {
                    throw new Error("Invalid number in diff_fromDelta: " + param);
                }
                var text = text1.substring(pointer, (pointer += n));
                if (tokens[x].charAt(0) == "=") {
                    diffs[diffsLength++] = new diff_match_patch.Diff(DIFF_EQUAL, text);
                } else {
                    diffs[diffsLength++] = new diff_match_patch.Diff(DIFF_DELETE, text);
                }
                break;
            default:
                // Blank tokens are ok (from a trailing \t).
                // Anything else is an error.
                if (tokens[x]) {
                    throw new Error("Invalid diff operation in diff_fromDelta: " + tokens[x]);
                }
        }
    }
    if (pointer != text1.length) {
        throw new Error(
            "Delta length (" +
                pointer +
                ") does not equal source text length (" +
                text1.length +
                ")."
        );
    }
    return diffs;
};

/**
 * Class representing one patch operation.
 * @constructor
 */
diff_match_patch.patch_obj = function () {
    /** @type {!Array.<!diff_match_patch.Diff>} */
    this.diffs = [];
    /** @type {?number} */
    this.start1 = null;
    /** @type {?number} */
    this.start2 = null;
    /** @type {number} */
    this.length1 = 0;
    /** @type {number} */
    this.length2 = 0;
};

/**
 * Emulate GNU diff's format.
 * Header: @@ -382,8 +481,9 @@
 * Indices are printed as 1-based, not 0-based.
 * @return {string} The GNU diff string.
 */
diff_match_patch.patch_obj.prototype.toString = function () {
    var coords1, coords2;
    if (this.length1 === 0) {
        coords1 = this.start1 + ",0";
    } else if (this.length1 == 1) {
        coords1 = this.start1 + 1;
    } else {
        coords1 = this.start1 + 1 + "," + this.length1;
    }
    if (this.length2 === 0) {
        coords2 = this.start2 + ",0";
    } else if (this.length2 == 1) {
        coords2 = this.start2 + 1;
    } else {
        coords2 = this.start2 + 1 + "," + this.length2;
    }
    var text = ["@@ -" + coords1 + " +" + coords2 + " @@\n"];
    var op;
    // Escape the body of the patch with %xx notation.
    for (var x = 0; x < this.diffs.length; x++) {
        switch (this.diffs[x][0]) {
            case DIFF_INSERT:
                op = "+";
                break;
            case DIFF_DELETE:
                op = "-";
                break;
            case DIFF_EQUAL:
                op = " ";
                break;
        }
        text[x + 1] = op + encodeURI(this.diffs[x][1]) + "\n";
    }
    return text.join("").replace(/%20/g, " ");
};


/**
 * @odoo
 * Export main object and attach useful variables
 */
exports.DiffMatchPatch = Object.assign(diff_match_patch, {
    DIFF_DELETE,
    DIFF_INSERT,
    DIFF_EQUAL,
});

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